// Copyright 2019-2023 Tauri Programme within The Commons Conservancy
// SPDX-License-Identifier: Apache-2.0
// SPDX-License-Identifier: MIT

use std::{collections::HashMap, future::Future, path::PathBuf, pin::Pin, string::FromUtf8Error};

use encoding_rs::Encoding;
use serde::{Deserialize, Serialize};
use tauri::{
    ipc::{Channel, CommandScope, GlobalScope},
    Manager, Runtime, State, Window,
};

use crate::{
    open::Program,
    process::{CommandEvent, TerminatedPayload},
    scope::ExecuteArgs,
    Shell,
};

type ChildId = u32;

#[derive(Debug, Clone, Serialize)]
#[serde(tag = "event", content = "payload")]
#[non_exhaustive]
pub enum JSCommandEvent {
    /// Stderr bytes until a newline (\n) or carriage return (\r) is found.
    Stderr(Buffer),
    /// Stdout bytes until a newline (\n) or carriage return (\r) is found.
    Stdout(Buffer),
    /// An error happened waiting for the command to finish or converting the stdout/stderr bytes to an UTF-8 string.
    Error(String),
    /// Command process terminated.
    Terminated(TerminatedPayload),
}

fn get_event_buffer(line: Vec<u8>, encoding: EncodingWrapper) -> Result<Buffer, FromUtf8Error> {
    match encoding {
        EncodingWrapper::Text(character_encoding) => match character_encoding {
            Some(encoding) => Ok(Buffer::Text(
                encoding.decode_with_bom_removal(&line).0.into(),
            )),
            None => String::from_utf8(line).map(Buffer::Text),
        },
        EncodingWrapper::Raw => Ok(Buffer::Raw(line)),
    }
}

impl JSCommandEvent {
    pub fn new(event: CommandEvent, encoding: EncodingWrapper) -> Self {
        match event {
            CommandEvent::Terminated(payload) => JSCommandEvent::Terminated(payload),
            CommandEvent::Error(error) => JSCommandEvent::Error(error),
            CommandEvent::Stderr(line) => get_event_buffer(line, encoding)
                .map(JSCommandEvent::Stderr)
                .unwrap_or_else(|e| JSCommandEvent::Error(e.to_string())),
            CommandEvent::Stdout(line) => get_event_buffer(line, encoding)
                .map(JSCommandEvent::Stdout)
                .unwrap_or_else(|e| JSCommandEvent::Error(e.to_string())),
        }
    }
}

#[derive(Debug, Clone, Deserialize, Serialize)]
#[serde(untagged)]
#[allow(missing_docs)]
pub enum Buffer {
    Text(String),
    Raw(Vec<u8>),
}

#[derive(Debug, Copy, Clone)]
pub enum EncodingWrapper {
    Raw,
    Text(Option<&'static Encoding>),
}

#[derive(Debug, Clone, Default, Deserialize)]
#[serde(rename_all = "camelCase")]
pub struct CommandOptions {
    #[serde(default)]
    sidecar: bool,
    cwd: Option<PathBuf>,
    // by default we don't add any env variables to the spawned process
    // but the env is an `Option` so when it's `None` we clear the env.
    #[serde(default = "default_env")]
    env: Option<HashMap<String, String>>,
    // Character encoding for stdout/stderr
    encoding: Option<String>,
}

#[allow(clippy::unnecessary_wraps)]
fn default_env() -> Option<HashMap<String, String>> {
    Some(HashMap::default())
}

#[inline(always)]
fn prepare_cmd<R: Runtime>(
    window: Window<R>,
    program: String,
    args: ExecuteArgs,
    options: CommandOptions,
    command_scope: CommandScope<crate::scope::ScopeAllowedCommand>,
    global_scope: GlobalScope<crate::scope::ScopeAllowedCommand>,
) -> crate::Result<(crate::process::Command, EncodingWrapper)> {
    let scope = crate::scope::ShellScope {
        scopes: command_scope
            .allows()
            .iter()
            .chain(global_scope.allows())
            .collect(),
    };

    let mut command = if options.sidecar {
        let program = PathBuf::from(program);
        let program_as_string = program.display().to_string();
        let program_no_ext_as_string = program.with_extension("").display().to_string();
        let configured_sidecar = window
            .config()
            .bundle
            .external_bin
            .as_ref()
            .and_then(|bins| {
                bins.iter()
                    .find(|b| b == &&program_as_string || b == &&program_no_ext_as_string)
            })
            .cloned();
        if let Some(sidecar) = configured_sidecar {
            scope.prepare_sidecar(&program.to_string_lossy(), &sidecar, args)?
        } else {
            return Err(crate::Error::SidecarNotAllowed(program));
        }
    } else {
        match scope.prepare(&program, args) {
            Ok(cmd) => cmd,
            Err(e) => {
                #[cfg(debug_assertions)]
                eprintln!("{e}");
                return Err(crate::Error::ProgramNotAllowed(PathBuf::from(program)));
            }
        }
    };
    if let Some(cwd) = options.cwd {
        command = command.current_dir(cwd);
    }
    if let Some(env) = options.env {
        command = command.envs(env);
    } else {
        command = command.env_clear();
    }

    let encoding = match options.encoding {
        Option::None => EncodingWrapper::Text(None),
        Some(encoding) => match encoding.as_str() {
            "raw" => {
                command = command.set_raw_out(true);
                EncodingWrapper::Raw
            }
            _ => {
                if let Some(text_encoding) = Encoding::for_label(encoding.as_bytes()) {
                    EncodingWrapper::Text(Some(text_encoding))
                } else {
                    return Err(crate::Error::UnknownEncoding(encoding));
                }
            }
        },
    };

    Ok((command, encoding))
}

#[derive(Serialize)]
#[serde(untagged)]
enum Output {
    String(String),
    Raw(Vec<u8>),
}

#[derive(Serialize)]
pub struct ChildProcessReturn {
    code: Option<i32>,
    signal: Option<i32>,
    stdout: Output,
    stderr: Output,
}

#[allow(clippy::too_many_arguments)]
#[tauri::command]
pub async fn execute<R: Runtime>(
    window: Window<R>,
    program: String,
    args: ExecuteArgs,
    options: CommandOptions,
    command_scope: CommandScope<crate::scope::ScopeAllowedCommand>,
    global_scope: GlobalScope<crate::scope::ScopeAllowedCommand>,
) -> crate::Result<ChildProcessReturn> {
    let (command, encoding) =
        prepare_cmd(window, program, args, options, command_scope, global_scope)?;

    let mut command: std::process::Command = command.into();
    let output = command.output()?;

    let (stdout, stderr) = match encoding {
        EncodingWrapper::Text(Some(encoding)) => (
            Output::String(encoding.decode_with_bom_removal(&output.stdout).0.into()),
            Output::String(encoding.decode_with_bom_removal(&output.stderr).0.into()),
        ),
        EncodingWrapper::Text(None) => (
            Output::String(String::from_utf8(output.stdout)?),
            Output::String(String::from_utf8(output.stderr)?),
        ),
        EncodingWrapper::Raw => (Output::Raw(output.stdout), Output::Raw(output.stderr)),
    };

    #[cfg(unix)]
    use std::os::unix::process::ExitStatusExt;

    Ok(ChildProcessReturn {
        code: output.status.code(),
        #[cfg(windows)]
        signal: None,
        #[cfg(unix)]
        signal: output.status.signal(),
        stdout,
        stderr,
    })
}

#[allow(clippy::too_many_arguments)]
#[tauri::command]
pub fn spawn<R: Runtime>(
    window: Window<R>,
    shell: State<'_, Shell<R>>,
    program: String,
    args: ExecuteArgs,
    on_event: Channel<JSCommandEvent>,
    options: CommandOptions,
    command_scope: CommandScope<crate::scope::ScopeAllowedCommand>,
    global_scope: GlobalScope<crate::scope::ScopeAllowedCommand>,
) -> crate::Result<ChildId> {
    let (command, encoding) =
        prepare_cmd(window, program, args, options, command_scope, global_scope)?;

    let (mut rx, child) = command.spawn()?;

    let pid = child.pid();
    shell.children.lock().unwrap().insert(pid, child);
    let children = shell.children.clone();

    tauri::async_runtime::spawn(async move {
        while let Some(event) = rx.recv().await {
            if matches!(event, crate::process::CommandEvent::Terminated(_)) {
                children.lock().unwrap().remove(&pid);
            };
            let js_event = JSCommandEvent::new(event, encoding);

            if on_event.send(js_event.clone()).is_err() {
                fn send<'a>(
                    on_event: &'a Channel<JSCommandEvent>,
                    js_event: &'a JSCommandEvent,
                ) -> Pin<Box<dyn Future<Output = ()> + Send + 'a>> {
                    Box::pin(async move {
                        tokio::time::sleep(std::time::Duration::from_millis(15)).await;
                        if on_event.send(js_event.clone()).is_err() {
                            send(on_event, js_event).await;
                        }
                    })
                }
                send(&on_event, &js_event).await;
            }
        }
    });

    Ok(pid)
}

#[tauri::command]
pub fn stdin_write<R: Runtime>(
    _window: Window<R>,
    shell: State<'_, Shell<R>>,
    pid: ChildId,
    buffer: Buffer,
) -> crate::Result<()> {
    if let Some(child) = shell.children.lock().unwrap().get_mut(&pid) {
        match buffer {
            Buffer::Text(t) => child.write(t.as_bytes())?,
            Buffer::Raw(r) => child.write(&r)?,
        }
    }
    Ok(())
}

#[tauri::command]
pub fn kill<R: Runtime>(
    _window: Window<R>,
    shell: State<'_, Shell<R>>,
    pid: ChildId,
) -> crate::Result<()> {
    if let Some(child) = shell.children.lock().unwrap().remove(&pid) {
        child.kill()?;
    }
    Ok(())
}

#[tauri::command]
pub fn open<R: Runtime>(
    _window: Window<R>,
    shell: State<'_, Shell<R>>,
    path: String,
    with: Option<Program>,
) -> crate::Result<()> {
    shell.open(path, with)
}